I'm hungover and can't do a child's maths homework...

[.....]

I have a 12 year old asking me for help with his homework. I can't do it. I'm hungover and tired and just want to play a bit of Forza.

Can someone tell me the formula that links these numbers as in x and y

X | Y
1 | 3
2 | 15
3 | 35
4 | 63
5 | 99

Yours shamefully,
Joe

[thegubner]

It's nearly certain to be something to do with numbers.


I'm NOT hungover.

[Mehty]

x goes up and so does y?
I should know this, but iv been out of school for 2 years now so its all gone
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2007 YBR 125 (sold), 2011 ER6-N (sold), LHD 1999 GSX750F (sold), ??????

[Poseidon]

2x squared - 1

Can't do super script on here.
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1977 Honda CG125
2002 Ducati Monster S4 (currently restoring)

[-Savage-]

got it, XxXx4-1=Y

X squared times 4 minus 1 = Y
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[.....]

Thanks guys

[Deckx]

mmm... whats the point of this type of maths

[SoND]

[Skudd]

I used it at the chip shop last night. Thanks to god I had a pencil and paper with me at the time otherwise I wouldn't have got an extra sausage and a tub of curry.
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[Poseidon]

Okay, this has been annoying me since I posted... The formula I suggested is this:

https://latex.codecogs.com/gif.latex?y=(2x)^{2}-1

Which, whilst correct, can be simplified to what savage wrote. I was dashing out of the door when I replied yesterday, so didn't spot this at the time! I personally would go with this formula (savages answer) as it looks neater not having the brackets:

https://latex.codecogs.com/gif.latex?y=4x^{2}-1
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1977 Honda CG125
2002 Ducati Monster S4 (currently restoring)

[Poseidon]

[SoND]

Deleted my post because I wanted to think about it for a while
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Go back to bed - You have no rights - "Streetfighters ~ Mainstream motorcycling's crackwhore sister."

[Poseidon]

Good job I quoted you then eh!
____________________
1977 Honda CG125
2002 Ducati Monster S4 (currently restoring)

[SoND]

When you're inputting it into a calculator you need to start putting the brackets in but when you're writing/reading it algebraically the coefficient takes priority over the index.

When you read "2x²" you're taking two of x and squaring the result of that.

(2 * x)² - 1 == 4(x²) - 1 - Nonsense.

EDIT:
You're right and I'm a dumbass.

Fuck
____________________
Go back to bed - You have no rights - "Streetfighters ~ Mainstream motorcycling's crackwhore sister."

[Poseidon]

It helps I'm doing this sort of stuff on a daily basis at the moment. Specifically using the exponent function for population changes over time (bacteria mostly).

@deckx:

As SoND said, it allows you to do all kinds of funky stuff like working out rates of change etc, but it also means you don't have to draw a graph to find the Nth term... For example, if you were asked to find y when x=7,563 for the formula in this thread. Whilst you could draw the graph to find the answer, you'd have to draw the x-axis to 7,563 and the y-axis to almost 230million (might be a little time consuming!). Using the formula, you can work out that when x=7,563, y=228,795,875 in a matter of seconds!
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1977 Honda CG125
2002 Ducati Monster S4 (currently restoring)

[st3v3]

Anybody else baffled by this stuff?

Also shamefully,

Steve.
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Roger wrote: Women don't get damp for clingy puppies. Get some better happy pills, hit the gym & buy a medallion the size of a dinner plate. Job done

[Whosthedaddy]

[swampy]

Well i got the answer from the original question... but then got very lost when people started putting into formulae... Looks like Egyptian hieroglyphics to me.
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[WildGoose]

[Poseidon]

[SoND]

[st3v3]

I always get stumped att he point where a letter equals a number; so X = 2 and Y = 5.

How the fook can a letter equate to a number? How do you 'just' allocate a number to a letter; what gives it a corresponding value?
____________________
Roger wrote: Women don't get damp for clingy puppies. Get some better happy pills, hit the gym & buy a medallion the size of a dinner plate. Job done

[LordShaftesbu...]

I had the exact same objections to algebra. In Primary 7.

[SoND]

Think of it as an undefined variable until we put something in it.

In the original question we know that "Y" is equal to 4x² - 1.

Y is defined, it's not empty, we know what it is. It's 4x² - 1!

What does this mean? On a 2D graph you have two axis, y (vertical) and x (horizontal). You can pick any point on the x-axis, say "I want to know what 'Y' is when I'm at this point." then find it out by using the definition of 'Y'.

Let's pick the number 0 on the x-axis. We are saying x = 0

We take '0' and substitute it into the original equation (put 0 everywhere it says 'x')

When x = 0
Y = 4(0²) - 1
Y = -1

When x = 1
Y = 4(1²) - 1
Y = 4 - 1
Y = 3

When x = 2
Y = 4(2²) - 1
Y = 4(4) - 1
Y = 16 - 1
Y = 15

and so on.
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Go back to bed - You have no rights - "Streetfighters ~ Mainstream motorcycling's crackwhore sister."

[SoND]